The fire started when an air conditioner suddenly burst into flames after being switched on, a spokesman of the bank said.
The flames were doused by 15 fire tenders after a four hour battle, fire officials said.
All the trapped persons were helped out by fire and rescue service personnel through the rear side of the building, they said.
An ATM machine, computers and other equipment in the bank was damaged and the actual loss was being ascertained, fire service personnel said.